Hi there,
I'm learning from PHP5 Power Programming by Gutmans, Bakken & Rethans and have come to p.58. The book says the output is:
Judy
Joe
However I get nothing from neither IE8 nor FF3 instead!
My machine is XP + PHP5 + Apache2.2. The error message is:
Catchable fatal error: Object of class Person could not be converted to string in C:\Program Files\...\PHP5 PP\58.php on line 24
Any clue?
Thanks in advance,
-hide2may
// Here is the source: - <html>
-
<title>PHP5 Power Programming</title>
-
<head>P.58</head>
-
<body>
-
<?php
-
-
error_reporting(E_ALL);
-
ini_set('display_errors', true);
-
-
class Person {
-
-
function _construct($name) {
-
$this->name = $name;
-
}
-
-
function getName() {
-
return $this->name;
-
}
-
-
private $name;
-
-
};
-
-
$judy = new Person("Judy") . "\n"; // <---- this is line 24
-
$joe = new Person("Joe") . "\n";
-
-
print $judy->getName();
-
print $joe->getName();
-
-
?>
-
</body>
-
</html>
10  1871 
the problem is - $judy = new Person("Judy") . "\n";
if you instantiate an object, you cannot apply any other operation at the same time. - // correct
-
$judy = new Person("Judy");
in your case the string concatenation forces new Person("Judy") to be converted to a string, which doesn’t work.
guess it’s a printing mistake, should probably be like in the previous example (and this would actually make sense) - $judy = new Person("Judy");
-
$joe = new Person("Joe");
-
print $judy->getName() . "\n";
-
print $joe->getName() . "\n";
and one additional note - $x = new Sample;
-
// is the same as
-
$x = new Sample();
@hide2may
since PHP runs on the server both browsers get the same output (unless you start working with HTTP/1.1* data (like Accept header…))
* see RFC 2616
However, you can have a __toString() implementation that will allow you to do what you attempt above (although I don't think it's quite the right way to do it). -
class Person {
-
-
private $person;
-
-
public function __construct($name) {
-
$this->person = $name;
-
}
-
-
public function __toString() {
-
return $this->person;
-
}
-
-
}
-
-
$person = new Person("mark") . " - hi";
-
-
echo $person;
-
Oh, no, Dormilich! Even I changed the relevant code to the followings, still get no display! How come?
...
$judy = new Person("Judy");
$joe = new Person("Joe");
print $judy->getName( );
print $joe->getName( );
@Markus
even book printers can make mistakes. I don’t think hide2may actually meant to do that.
No, Dormilich, I don't want to do Markus' way which is too far for me as a PHP beginner. My problem now becomes that even I changed those 4 lines mentioned by Dormilich in post 2, I still don't get the desired output, though the error message has gone. So, how do I proceed? Thanks again ^.^
The 4 lines have already been changed to:
$judy = new Person("Judy");
$joe = new Person("Joe");
print $judy->getName( ) . "\n";
print $joe->getName( ) . "\n";
Ah... the same thing happens again in p.70!
The book says the output is:
In Ancestor constructor
In Child constructor
But in my machine: No desired display, no error message!
I doubt that it has something to do with _construct( )
any ideas, please?
// Here is the code: - <html>
-
<title>PHP5 Power Programming</title>
-
<head>P.70</head>
-
<body>
-
<?php
-
-
error_reporting(E_ALL);
-
ini_set('display_errors', true);
-
-
class Ancestor {
-
const NAME = "Ancestor";
-
function _construct() {
-
print "In " . self::NAME . " constructor\n";
-
}
-
}
-
-
class Child extends Ancestor {
-
const NAME = "Child";
-
function _construct() {
-
parent::_construct();
-
print "In " . self::NAME . " constructor\n";
-
}
-
}
-
-
$obj = new Child();
-
?>
-
</body>
-
</html>
all the magical methods (__construct(), __destruct(), __get(), __set(), __call(), …) are written with 2 underscores in the beginning.
for the correct syntax also refer to the manual
PS: please use [code] [/code] tags when posting code
Easy mistake - magic methods use two preceding underscores. -
public function __construct()
-
-
// not!
-
public function _construct()
-
okay, that works!
thanks man \O/
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